A variety of materials or systems with variable light transmitting qualities are known, including electrochromic materials, suspended particle displays or screens, electrochromic, photochromic and thermochromic materials, and those that are hybrid—having two or more of photo-, electro- or thermochromic qualities. The materials may vary from solid, liquid, gel or the like, the particular state and composition of the material may be dependent upon, or limited by, the needs of the particular system. For example, the material may need to be conductive or insulative, may need to solubilize all components or only selected components of the system, and may further need to be tolerant of chemical transitions occurring with the material to achieve the light transmitting qualities. The chemical, electrochemical or molecular environments that may be suitable may vary greatly with the specific needs of the system.
Polymers may be used in such materials to provide structure or support, modulate rheology to aid in handling or manufacture, or to render the material in a suitable shape (e.g. be cast, extruded, coated or molded). Selection of the polymer(s) may be dependent on the intended use of the material, or in view of particular desired characteristics (e.g. photochemically inert, sufficiently high, or low, glass transition temperature, or the like.
The flowability of some polymer-containing systems may be modified by heat. While this may be advantageous for some manufacturing processes (e.g. injection molding, casting or the like), if the molded or cast material is subjected to temperature variations when in use, this characteristic may be undesirable in the final product.
A material that does not flow or alter shape with heat may be useful for some applications—resistance to flow may be imparted to a material by increasing the viscosity of the material, or solidifying the matrix, e.g. by crosslinking of one or more polymer species within the material. A variety of methods are generally known for creating intermolecular cross-linkages of polymers. Selection of a method, and/or particular reactants, may be dependent on an intended use or function, or desired characteristics of the composition or material comprising the cross-linked polymer, function of other components in the composition or the like. For example, some methods may include a condensation reaction, which may produce water, an alcohol group, an amine group or the like. Depending on the uses, the presence of these groups may adversely affect the durability or performance of the composition, or the function of another component in the composition.
It may be advantageous to incorporate materials with variable light transmitting qualities into laminated glass (“safety glass”). Some of these materials may be degraded, or some aspect of performance reduced, when subjected to the temperature and pressure of conventional glass lamination.